The whole config object and initConfig was never fully flushed out and used by the framework. I think this is a case where there is a bug but since we don't have the config system full working it was never caught.

The columnLines config is what is tripping it up. Ext.grid.Panel has gone under a lot of changes in 4.1.0 so this looks to be fixed in 4.1.0 RC3 and I would recommend trying to update to 4.1.0 RC3 but here is an override that is working for me in 4.0.7: